Consider the following scenario...
1. Two Active Directory forests (Forest1 + Forest2) are being audited by Change Auditor in "multi-forest" configuration (Coordinators in each forest + shared ChangeAuditor database).
2. An Active Directory account which belongs to Forest1 is added to "Account Exclusions" template from and added to the configuration.
3. Changes performed by the excluded account in Forest1 are excluded as expected. Changes performed by the excluded account in Forest2 are audited while they are expected to have been excluded.
Specify the account which must be excluded across multiple forests on the 3rd screen of the Excluded Accounts Wizard ("Select Accounts to exclude using Wildcards") using domain\username format. These accounts will be passed to any agent regardless of forest and the events will be excluded as expected across all forests.
Waiting fix in a future release of Change Auditor.